The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Galium Nitrite (GaN) has been the most studied material for optoelectronic applications among all III-V nitrides. The heteroepitaxial growth and doping problem have been two obstacles that had to be overcome for the realization of blue LEDs and lasers made of GaN. Gallium nitride substrates are typically grown on sapphire Al2O3, 6H—SiC and ZnO utilizing metalorganic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE) or hydride vapor phase epitaxy (HVPE). Most as grown GaN (and InN) films exhibited high n-type conductivity due to native defects with no p-type conductivity. P-type GaN can be obtained by doping GaN with Mg, thereby creating GaN p-n homojunctions that can be used to provide blue light emitting diodes (LEDs), which are now being made commercially. However, GaN has only been doped successfully to produce such p-n homojunctions in films with a small amount of Al (x˜0.1 for p-type and x<0.4 for n-type).
Aluminum nitride (AlN) has a very wide band-gap, a high thermal conductivity, high electrical resistivity, high acoustic velocity, high thermal stability, and high chemical resistance and radiation stability. These properties make AlN suitable for ultraviolet (UV) optical devices, surface acoustic wave (SAW) devices, electrical insulators or passive layers in microelectronics. Such devices can operate in a harsh environment with high temperatures and/or radiation. However, as grown, AlN films do not show any n-type or p-type characteristics and because of the very wide band gap of AlN, such AlN devices are very difficult to dope with impurities to make n-type and/or p-type semiconductors.